Error performance of OTFS in the presence of IQI and PA Nonlinearity

Abstract

Orthogonal time frequency space (OTFS) modulation, which was proposed recently is a two dimensional modulation technique designed in the delay-Doppler (DD) domain unlike OFDM which was designed in the time-frequency (TF) domain. It is suited for doubly dispersive fading wireless channels. Some transformations are done at the transmitter and receiver of the conventional multicarrier modulation. In this paper, we pre- distort frequency dependent transmitter (Tx) IQ imbalance (IQI) and power amplifier (PA) nonlinearity in two steps. The bit error rate performance analysis of OTFS in the presence of receiver (Rx) IQI along with residual Tx IQI is analyzed. We develop an input-output relation of OTFS in the DD domain, with impairments in the presence of time varying (TV) channel. A message passing algorithm is used to detect the OTFS signal with impairments. We show that compensating IQI at the Tx and PA non-linearity has improved the BER performance.